1. Field of the Invention
This invention generally relates to a duplex electrical grounding receptacle and, more particularly, to a grounding arrangement assembled within the receptacle and enabling an installer to terminate, in either a wrap-around or push-in manner, a grounding wire to a one-piece, multi-function, grounding strip.
2. Description of Related Art
A conventional grounded duplex electrical receptacle had a pair of electrical outlets, each having two power sockets for receiving two power prongs of an electrical plug, and one grounding socket for receiving a grounding prong of the plug. The receptacle was conventionally installed in a wall-mounted electrical junction box to which two power wires and a ground wire were routed from a power supply. Each wire was connected to a respective screw mounted on the receptacle. Each screw was threaded into, and made electrical contact with, a respective electrically conductive strip located within the receptacle. Thus, a first power strip spanned the distance between, and interconnected, associated power sockets of both outlets; a second power strip spanned the distance between, and interconnected, other associated power sockets of both outlets; and a grounding strip spanned the distance between, and interconnected, associated grounding sockets of both outlets.
A conventional wall plate was mounted over the receptacle. The wall plate, which could be made of metal or plastic, had openings corresponding to the spacing and size of the electrical outlets so that the outlets remained exposed after the wall plate had been mounted over the receptacle. The exposed outlets enabled the three-pronged electrical plugs to be inserted into the corresponding sockets of the outlets.
As previously noted, a grounding screw was threaded into the grounding strip. The ground wire at the junction box was exposed at its end and wrapped at least partly underneath the head of the grounding screw to provide a reliable grounding for the receptacle. The grounding screw was subject to external forces, particularly during wiring of the receptacle, which forces tended to pull the grounding screw from its grounding strip. To prevent such removal, most grounding strips according to the prior art were typically made of a metal having a thickness of at least 0.030 in. and extruded to a 1/16 in. long cylinder in order to provide a minimum of two threads at 32 threads per inch, for engaging the grounding screw. Two threads were considered the minimum necessary to withstand expected removal forces when the screw was torqued down on the wire with a rotational force of 14 in.-lbs.
However, such thick grounding strips were undesirable in that the relatively large thickness dimension of the grounding strips contributed to high manufacturing costs. Also, they generally were made up of at least two parts: thick metal for the screw grounding terminal and thin metal for the female sockets. Also, fasteners were employed to reliably fasten the two parts.
Another problem with the known grounding strips was that they typically had to be held in position between upper and lower housing parts of the receptacle during assembly therewith. Experience showed that the grounding strip was sometimes shifted in position, thereby misaligning the strip and complicating the overall assembly procedure.
It was proposed in U.S. patent application Ser. No. 208,178, filed June 17, 1988, now Pat. No. 4,836,793 the entire contents of which are hereby incorporated herein by reference herein, and assigned to the same assignee as the instant application, to reduce the thickness of the grounding strip without compromising the ability of the grounding screw to reliably resist removal therefrom due to external forces. To that end, a thinner grounding strip with an integral screw terminal was proposed. The terminal included two spaced-apart grounding plates, each having a stamped-through single screw thread bounding a hole. A grounding screw was inserted through respective holes, and the single screw threads threadedly engaged the screw at spaced-apart locations to resist removal due to external forces.
Although the invention disclosed in said application was very satisfactory for the purpose, among others, of reducing the thickness of the grounding strip, only one type of grounding termination was available to an electrician. The grounding wire was wrapped around the shaft of the grounding screw and clamped by the screw head against the strip to complete the grounding connection. This wrap-around installation technique, however, has proved to be somewhat labor-intensive and time-consuming, particularly when a multitude of electrical receptacles were required to be wired. It would be desirable to present the electrician with the option of terminating a grounding wire to the grounding strip in a manner other than the aforementioned wrap-around technique.